Retro-reflective multi-port filter device with triple-fiber ferrule

Abstract

A retro-reflective multi-port fiber optic device ( 100 ) includes the triple-fiber ferrule ( 10 ) with a GRIN rod lens ( 12 ) to couple the light. The triple-fiber ferrule ( 10 ) with three fibers ( 18, 20, 22 ) thereof is attached to the angled facet of the GRIN rod lens ( 12 ) and the WDM filter ( 14 ) is attached to the opposite side of the lens ( 12 ). A reflective mirror ( 16 ) is attached next to the other side of the WDM filter ( 14 ) opposite to the lens ( 12 ) after alignment. The triple-fiber ferrule ( 10 ) is used to couple light in and out of the device, and tune the thin film filter center wavelength to the desired ITU grid. Therefore, the coupled-in light from the common input pigtail fiber ( 18 ) of the triple-fiber ferrule ( 10 ) will be collimated and transmitted unto the WDM filter ( 14 ) wherein the part of the in-pass-band light with regard to the WDM filter ( 14 ) will transmit through the WDM filter ( 14 ), and then successively retro-reflect back by the mirror ( 16 ) and further transmit through the WDM band-pass filter ( 14 ) again. The retro-reflected in-pass-band signal is then coupled into one retro-reflective transmission output fiber/port ( 22 ) of the triple-fiber ferrule ( 10 ) as a demultiplexed channel. On the other hand, the out-pass-band light with regard to the WDM filter will not transmit through the WDM filter ( 14 ) to interact with the mirror ( 16 ), but instead be directly reflected back by the WDM filter ( 14 ) and coupled into a reflection output fiber/port ( 20 ) of the triple-fiber ferrule ( 14 ) to be transmitted to the next stage for further demultiplexing other channels.

We claim:  
     
       1. An optic fiber device comprising: 
       a triple-fiber ferrule;  
       three fibers disposed in the ferrule and including a common input fiber, a reflection output fiber and a retro-reflective transmission output fiber;  
       a lens positioned by the ferrule;  
       a WDM filter positioned by the lens opposite to the ferrule; and  
       a mirror positioned by the filter opposite to the lens; whereby  
       an in-pass-band light enters the device via the common input fiber and leaves the device via the retro-reflective transmission output fiber, while an out-pass-band light enters the device via the common input fiber and leaves the device via the reflection output fiber; wherein  
       an incidence angle of said in-pass-band light via the common input fiber relative to the filter is generally equal to another incidence angle of said in-pass-band light via the mirror.  
     
     
       2. The device as defined in  claim 1 , wherein the input fiber and the two output fibers extend out of the ferrule from a same side thereof. 
     
     
       3. The device as defined in  claim 1 , wherein centers of the three fibers are arranged to be located on a same circumference, and the center of the input fiber and the center of the reflection output fiber are respectively positioned at two opposite ends of a corresponding diameter of said circumference. 
     
     
       4. The device as defined in  claim 3 , wherein said circumference defines a circle center, and the centers of said three fibers cooperate with said circle center to form a T-shaped configuration. 
     
     
       5. The device as defined in  claim 4 , wherein said circle center is substantially coincident with an optical axis of the lens. 
     
     
       6. The optical fiber device as defined in  claim 1 , wherein a spacer is positioned between the ferrule and the lens. 
     
     
       7. The optical fiber device as defined in  claim 1 , wherein WDM coating film for demultiplexing is applied to the surface of the filter away from the lens for easy access to another component positioned by said filter opposite to said lens. 
     
     
       8. An optic fiber arrangement comprising: 
       a ferrule;  
       at least an input fiber and a retro-reflective transmission output fiber disposed in the ferrule;  
       a lens positioned the ferrule;  
       a WDM filter positioned the lens opposite to the ferrule; and  
       a mirror positioned the filter; wherein  
       an in-pass-band light enters the device via the input fiber and passes through the filter to reach the mirror, and is successively reflected back to the filter and enters the retro-reflective transmission output fiber and leaves the device as a demultiplexed channel, whereby said light double passes the filter before leaving the device; wherein  
       centers of the three fibers are arranged to be located on a same circumference, and the center of the input fiber and the center of the reflection output fiber are respectively positioned at two opposite ends of a corresponding diameter of said circumference.  
     
     
       9. The device as defined in  claim 8 , wherein the input fiber and the retro-reflective transmission output fiber are located on a same side of the device. 
     
     
       10. An optic fiber device comprising: 
       a ferrule;  
       at least one fiber disposed in the ferrule;  
       a lens positioned by the ferrule; and  
       a WDM filter positioned by the lens opposite to the ferrule, said filter defining two opposite side surfaces; wherein  
       WDM coating film for demultiplexing is applied to the surface of the filter away from the lens for easy access to another component positioned by said filter opposite to said lens.  
     
     
       11. The device as defined in  claim 10 , wherein a spacer device is positioned between the lens and the ferrule. 
     
     
       12. An optic fiber device arrangement with two reflections thereof, comprising: 
       a ferrule;  
       a plurality of fibers disposed in the ferrule;  
       a lens positioned by the ferrule;  
       a WDM filter positioned by the lens opposite to the ferrule; and  
       a mirror positioned by the filter opposite to the lens; wherein  
       an in-pass-band light passes the filter and is retro-reflected backwardly by the mirror while an out-pass-band light passes the filter and is directly reflected backwardly by coating film of the filter; wherein  
       said circumference defines a circle center which is substantially coincident with an optical axis of the lens where reflection occurs.  
     
     
       13. An optic fiber arrangement comprising: 
       a triple-fiber ferrule;  
       three fibers disposed in the ferrule and including at least an input fiber, a reflection output fiber and a retro-reflective transmission output fiber;  
       a lens positioned by the ferrule;  
       a WDM filter positioned by the lens opposite to the ferrule; wherein  
       an in-pass-band light enters the device via the common input fiber and leaves the device via the retro-reflective transmission output fiber, while an out-pass-band light enters the device via the common input fiber and leaves the device via the reflection output fiber, and both light travel the corresponding output fibers along a same direction which is away from the filter; wherein  
       centers of the three fibers are arranged to be located on a same circumference, and the center of the input fiber and the center of the reflection output fiber are respectively positioned at two opposite ends of a corresponding diameter of said circumference.  
     
     
       14. The arrangement as defined in  claim 13 , wherein a mirror is positioned by the WDM filter opposite to the lens.